This application claims the benefit of priority of German Patent Application 101 33 967.1 filed Jul. 17, 2001.
The invention relates to a fuel tank for a motor vehicle, and in particular, to a motor vehicle with a feed unit provided for sucking in fuel from a baffle, and with a suction jet pump for feeding fuel into the baffle.
Fuel tanks are often used in present-day motor vehicles and are known from practice. In this context, the suction jet pump serves, as a rule, for feeding fuel out of a chamber remote from the baffle. This ensures that the baffle is consistently filled with fuel when the fuel tank is virtually empty. Emptying of the baffle may lead to the feed unit running dry and consequently to its destruction.
One disadvantage, however, is that present-day fuel tanks often have a very shallow and wide configuration. The baffle is therefore very low. Hence, when the motor vehicle is cornering, there is a the risk that fuel will flow out of the chamber having the suction jet pump and the feeding of the suction jet pump will cease. The baffle may consequently be emptied quickly.
The problem on which the invention is based is to design a fuel tank of the type initially mentioned, such that the feed unit is reliably prevented from running dry.
In one embodiment of the invention, an intermediate tank is arranged between the suction jet pump and the baffle, the intermediate tank configured for the intermediate storage of the fuel fed by the suction jet pump and for conducting the fuel into the baffle.
In one aspect of the invention, the intermediate tank is first filled with fuel. This fuel subsequently flows into the baffle. Consequently, even in the case of very small baffles, the constant filling of these with fuel can be ensured. The feed unit can be reliably prevented from running dry by virtue of the invention.
Often, in motor vehicles with high-powered internal combustion engines, a plurality of feed units are used in a corresponding number of baffles. Peak consumption of the internal combustion engine are thereby covered. The feed units each supply a suction jet pump arranged in remote regions of the fuel tank. In the conventional fuel tank, each of the suction jet pumps serves for filling one of the baffles. However, this configuration leads to one of the feed units running dry when the associated suction jet pump is no longer covered with fuel. It is conceivable for each of the suction jet pumps to be connected to an intermediate tank. However, according to an advantageous embodiment of the invention, a contribution to a further increase in the reliability of the supply of fuel to the feed units is made when a plurality of baffles and suction jet pumps are connected in each case to a common intermediate tank. In this configuration, virtually any desired number of suction jet pumps can be arranged, distributed, in various chambers of the fuel tank according to the invention. The additional tank is constantly filled with fuel when at least one of the suction jet pumps is covered by fuel. The connection of the intermediate tank to the baffles in which feed units are arranged ensures that the feed units are constantly supplied with fuel. Consequently, an emergence of a suction jet pump or of a few suction jet pumps does not lead to an interruption in the filling of the intermediate tank and therefore of the baffles.
According to another advantageous embodiment of the invention, a constant filling of the baffles can be ensured in a simple way when the intermediate tank is arranged above the baffles.
The intermediate tank could, for example, be open upwardly, so that it can overflow. However, according to another advantageous embodiment of the invention, an unnecessary circulation of fuel fed via the suction jet pumps can be avoided in by a device for generating an intended dynamic pressure in the intermediate tank as a function of the filling level of the latter. The power of the suction jet pump is thereby regulated by the dynamic pressure, so that, with the intermediate tank filled, its further filling can be avoided. The circulation consequently avoided leads to a particularly low permeation of the fuel tank according to the invention.
According to another advantageous embodiment of the invention, the device for generating an intended dynamic pressure is configured in structural terms when the intermediate tank is closed and when an overflow of the intermediate tank has a throttle. The throttle may be of virtually any desired configuration and at an intended pressure automatically switch the overflow or be open solely when there is air in the upper region of the intermediate tank and close upon contact with fuel. Moreover, the intermediate tank can therefore be vented via the throttle.
According to another advantageous embodiment of the invention, a completely wear-free control of the power of the suction jet pump or of the suction jet pumps can be produced in when a delivery line for the fuel fed by the suction jet pump or the suction jet pumps is arranged in the lower region of the intermediate tank. The dynamic pressure thereby rises in proportion to the filling level in the intermediate tank.
In the case of transverse accelerations of the fuel tank according to the invention, a filling of the baffles is ensured when discharge lines leading to the baffles are arranged in the lower region of the intermediate tank. In the case of particularly sharply angled fuel tanks according to the invention and the intermediate tanks having a dynamic pressure, a routing of the fuel out of the intermediate tank into the baffles can be ensured, even counter to transverse acceleration forces, when throttles and/or non-return valves are arranged in the discharge lines leading to the baffles.
According to another advantageous embodiment of the invention, the baffles are filled with fuel, even when the intermediate tank is virtually empty, when the lower region of the intermediate tank has a funnel-shaped configuration.
A quantity of fuel sufficient for the baffles is constantly collected in the bottom region of the intermediate tank at the discharge lines to the baffles when an angle xcex1 of the funnel-shaped region of the wall to the cross section of the intermediate tank is equal to the arc tangent of the transverse acceleration to the gravitational acceleration.
The fuel tank according to the invention has a configuration in structural terms when the overflow of the intermediate tank has a tube passing through the funnel-shaped region of the wall and when the tube is connected to at least one of the baffles.
According to another advantageous embodiment of the invention, a contribution to a further reduction in the circulation of the fuel is made when a return line of an internal combustion engine of the motor vehicle is led into the intermediate tank.
In one aspect of the invention, device generating an intended dynamic pressure in the baffle or the baffles contribute to a further reduction in the circulation of the fuel and therefore to a reduction in the permeation of fuel through the wall of the fuel tank according to the invention.
In another aspect of the invention, the number of lines to be laid within the fuel tank can be kept particularly low when a plurality of feed units have a common distributor for lines leading to the suction jet pumps and a forward-flow line leading to the internal combustion engine.